1. Field of the Invention
This invention relates to an adhesion improving agent, and more particularly to an adhesion improving agent useful for improving the adhesion between a metal and a silicone rubber.
2. Description of the Prior Art
Silicone rubbers are used for a wide variety of purposes, because of their excellent properties. The silicone rubbers are also used in the form of a composite obtained by adhesion of a silicone rubber to a metal. In producing such a composite, it is a common practice to pretreat the surface of the metal with a primer in order to achieve firm adhesion between the silicone rubber and the metal.
As the primer, there have been proposed a composition comprising an alkoxysilane having an unsaturated bond or a hydrolysis-condensation product thereof or a co-hydrolysis-condensation product of two or more alkoxysilanes, a titanic acid ester, and a metal salt of an organic fatty acid [Japanese Patent Publication (KOKOKU) Nos. 62-17622 (1987) and 62-17623 (1987)]; a composition comprising an alkoxysilane having an unsaturated bond or a hydrolysis-condensation product thereof or a co-hydrolysis-condensation product of two or more alkoxysilanes, a titanic acid ester, a metal salt of an organic fatty acid, and an organosilicon compound having a Si-H radical [Japanese Patent Publication (KOKOKU) No. 61-2107 (1986)]; a rubber-like composition comprising a vinyl group-containing organopolysiloxane, a polysiloxane resin, an alkoxysilane, an organic peroxide, and a titanic acid ester [Japanese Patent Publication (KOKOKU) No. 56-39817 (1981)], and so on.
In the processes of adhering a silicone rubber and a metal to each other by use of the conventional primers, however, a complicated adhering operation has been required; for instance, an air-drying or baking step has been essentially required for evaporating off a solvent to solidify the primer, after application of the primer to the adherend. Furthermore, the conventional primers contain the hydrolysis-condensation product, a catalyst or a solvent, which may cause a safety problem in the preparation of the primers.